Enhancing the Impact Properties of Tin-Copper and Tin-Copper-Nickel Lead-Free Solders with Trace Additions of Zinc, Indium and Gold

Abstract: Lead-free solders based on the tin-copper-nickel system are well established in the electronics manufacturing industry as a cost-effective alternative to tin-silver-copper alloys where their particular combination of properties provides an advantage. While their compliance and stable intermetallic ensure that they have good resistance to impact loading increasing demands for even better performance are prompting the investigation of ways in which their mechanical properties can be further enhanced. This paper reports the preliminary results of a study into the effect of trace additions of zinc, indium and gold to tin-copper and tin-copper-nickel eutectic alloys on the resistance to shear impact at speeds of up to 4m/sec. These elements were chosen on the basis of reports of their stabilization of the hexagonal form of the Cu6Sn5 intermetallic.